Sub-250g Drone Altitude Limit in the UK

The 400ft Rule Applies to Every Drone

One of the most common misconceptions among new drone pilots is that lighter drones can fly higher. This is not the case. The CAA imposes a universal 400ft (120m) altitude ceiling on all unmanned aircraft operating in the Open Category, whether your drone weighs 50g or 24.9kg.

This altitude is measured above ground level (AGL), not above sea level. If you are standing on a hill that is 500ft above sea level, your drone may still climb 400ft above your position. However, you must remain aware of how your altitude relates to surrounding terrain and any nearby airspace restrictions.

Why 400ft Is the Ceiling

The 400ft limit exists to keep drones well separated from manned aircraft. In the UK, manned aircraft are generally required to fly above 500ft over open areas and 1,000ft over congested areas. The 400ft drone ceiling creates a safety buffer between drone operations and the lowest altitudes used by conventional aviation.

Breaching this limit is not merely a regulatory infraction. At altitudes above 400ft, your sub-250g drone enters airspace routinely used by helicopters, light aircraft, and air ambulances. A collision between a drone and a manned aircraft could have catastrophic consequences.

How Your Drone Measures Altitude

Most consumer drones measure altitude using a barometric pressure sensor, which tracks changes in air pressure relative to the take-off point. This means your drone displays height above the take-off location, not necessarily above the ground directly beneath it.

This distinction matters when flying over uneven terrain. If you take off from a valley floor and fly towards a hill, the ground beneath your drone may rise while your displayed altitude remains unchanged. In this scenario, your actual height above the ground could be much less than shown on screen, or you could inadvertently breach 400ft AGL over lower terrain nearby.

Key points to remember about altitude measurement:

• Barometric sensors can drift slightly during long flights due to changing weather conditions.
• GPS altitude readings are generally less precise than barometric readings and should not be relied upon as your primary altitude reference.
• Some drones offer terrain-following modes, but these require accurate terrain data and may not function reliably in all areas.

Exceptions to the 400ft Limit

There are very limited circumstances in which you may fly above 400ft in the UK:

• Within 50m of a tall structure: If you are inspecting a structure taller than 400ft (such as a telecommunications mast or wind turbine), you may fly up to 50m above the top of that structure. This exception is specifically for operations close to the structure itself.
• Specific Category operations: If you hold an Operational Authorisation from the CAA under the Specific Category, the authorisation may permit flights above 400ft under defined conditions. This requires a detailed risk assessment and is not available to Open Category pilots.

For the vast majority of sub-250g drone pilots flying recreationally or commercially in the Open Category, the 400ft limit is absolute.

Altitude Restrictions Near Airports

Near airports and aerodromes, altitude restrictions may be even more stringent than the standard 400ft ceiling. Flight Restriction Zones (FRZs) around airports typically impose lower altitude limits or prohibit drone flights entirely.

Being sub-250g does not exempt your drone from FRZ rules. If you are flying within an FRZ, you must comply with all restrictions regardless of your drone weight. Always check the NATS Drone Assist app or the CAA drone map before flying anywhere near an airport.

Penalties for Exceeding the Altitude Limit

Flying above 400ft without authorisation is an offence under the Air Navigation Order 2016. Penalties can include:

• An unlimited fine upon conviction.
• Potential imprisonment for reckless or dangerous flying that endangers aircraft.
• Seizure of your drone equipment.
• Revocation of your Flyer ID and Operator ID.

The CAA and police take altitude breaches seriously, particularly near airports and in controlled airspace. Several prosecutions have resulted from pilots flying drones well above the 400ft limit.

How to Stay Compliant

• Set your drone maximum altitude in its app settings to 120m (400ft) before every flight.
• Be aware of terrain changes. If the ground elevation drops as you fly, your height AGL increases.
• Never rely solely on your drone display. If in doubt, bring the drone lower.
• Check for NOTAMs (Notices to Airmen) that may impose temporary altitude restrictions in your area.
• Remember that windy conditions at higher altitudes may exceed your small drone ability to maintain position or return home safely.